1. Field of the Invention
Embodiments of the present application relate to a device and method for attaching to bones, for example to repair spinal compression fractures and to provide fixation to adjacent vertebra, and methods of using the same.
2. Description of the Related Art
Broken bones, such as compression fractures of one or more vertebrae in the spine, may be treated with internal fixation. Any indication needed spinal stability can also be treated by internal fixation. Examples include scoliosis, kyphosis, spondylothisthesis and rotation, segmental instability, such as disc degeneration and fracture caused by disease and trauma and congenital defects, and degeneration caused by tumors.
As shown by FIG. 1, internal fixation in the spine is often accomplished by first screwing fixation screws into the pedicles and vertebral bodies of the vertebrae 10. FIG. 2 shows that the fixation screws are then typically attached to a rigid fixation rod or plate that provide support between one or more weakened vertebra 10. This support often immobilizes the vertebra 10 to which the fixation screws have been inserted.
FIG. 3 illustrates that existing fixation systems often have the fixation rod 14 or plate, through which a number of fixation screws 12 are deployed. The screw head 18 prevents the fixation rod 14 from separating from the fixation screw 12. The fixation screw 12 also has a screw body 16 which has a screw longitudinal axis 20 often static relative to the fixation rod 14.
FIG. 4 illustrates that in some existing fixation systems, the fixation screws 12 can be polyaxial screws attached to the fixation rod 14 or plate in a manner so that the screw longitudinal axis 20 can rotate, as shown by arrows, with respect to the fixation rod 14.
Many patients are not candidates for existing fixation systems described above due to compression fractures in the vertebra. In these cases, if the screw is placed in the fracture, the bones can fail and the fixation screws 12 can be ripped from the bone resulting in complete failure and additional damage to the bone.
Vertebroplasty is often used to treat compression fractures in the vertebra, such as those caused by osteoporosis, cancer, or stress. Vertebroplasty is an image-guided, minimally invasive, nonsurgical therapy for injecting an orthopedic cement mixture through a needle into the fractured bone. The mixture fills or substantially fills the cavity of the compression fracture and is limited to certain chemical compositions, thereby limiting the amount of otherwise beneficial compounds that can be added to the fracture zone to improve healing. In an alternative procedure known as kyphoplasty, a balloon is first inserted in the compression fracture and the vertebra is expanded before the cement is injected into the newly formed space.
It would be desirable to provide a fixation screw can provide a higher anchoring force in vertebra having compression fractures, minimize bone failure and substantially eliminate the risk of backout.